Real Dictionary

vibrato
variable noun: Vibrato is a rapidly repeated slight change in the pitch of a musical note. Singers and musicians use vibrato to make the music sound more emotional.

vibrato in American English
a pulsating effect, less extreme than a tremolo, produced by rapid alternation of a given tone with a barely perceptible variation in pitch, as by the slight oscillation of the finger on a violin string or by a slight wavering of the tone in singing
noun: a pulsating effect, produced in singing by the rapid reiteration of emphasis on a tone, and on bowed instruments by a rapid change of pitch corresponding to the vocal tremolo

vibrato in British English
noun: a slight, rapid, and regular fluctuation in the pitch of a note produced on a stringed instrument by a shaking movement of the hand stopping the strings